Breast cancer is a cancer that forms in breast cells. It usually originates through the mutation of cells in the lining of the milk ducts and lobules in the breasts. It is the most common cancer in women and it can occur in men too. There are 2 broad types of cancer; the non-invasive breast cancer and invasive breast cancer.
The non-invasive breast cancer cells are contained within the milk ducts. However, if left untreated, the cancer cells can break out of the milk ducts and spread out, thus becoming an invasive breast cancer.
The invasive breast cancer cells spread outside the milk ducts or the lobules. These cancer cells will first spread to the surrounding breast tissue, move into the lymph nodes or blood stream and then travel to other parts of the body. The most common parts that the cancer cells travel to are the lungs, liver and bone.